The present invention relates to an improved image forming apparatus, including copying apparatuses or facsimiles.
Among the prior art image forming apparatuses, a major drawback of a copying apparatus which is rigged with an automatic original document feeder is as follows. In response to the start-up operation for copying, an original document which has already been set is fed to a predetermined position by the automatic document feeder. A detector detects the arrival of the original document at that predetermined position. Then, a scanning section for optically scanning the original document starts a scanning-ready-operation. Upon completion of the scanning-ready-operation, the scanning section starts an effective scanning of the original document.
Effective scanning is defined as that process whereby the original document is optically scanned from one side to the other in obtaining image information contained on the original document. In the scanning-ready-operation, an exposure lamp for effective scanning is lit and the movement of the mechanical moving portion associated with the scanning section, which portion contains the exposure lamp and a mirror, is started. The copy apparatus is further provided with a photosensitive drum which directly receives the light beams from the scanning section containing the optical information on the original document, to form thereon a visible image based on the optical information. A paper feeding device is also contained in the copy apparatus for feeding a sheet of paper, onto which the visible formed image is transferred, toward the photosensitive drum. The conventional copy apparatus is so designed that paper feeding starts after the arrival of the original document at the predetermined position is detected. In the specification, the operation, whereby the paper feeding device feeds the paper to a predetermined location on the photosensitive drum, will be referred to as an image-forming-ready-operation.
A fixed time elapses from the instant the exposure lamp is energized till the intensity of light from the lamp is increased so as to be in a stationary state. Until the moving portions associated with the scanning section reach a predetermined position, the scanning section also takes a fixed period of time. Thus, the scanning-ready-operation and the image-forming ready-operation continue for their respective fixed periods.
As described above, in the prior art copying apparatus provided with an automatic original document feeder, the scanning-ready-operation and the image-forming-ready operation are started after the original document reaches a predetermined position. Thus, in the conventional copying apparatus, an actual copying operation or an effective scanning operation cannot be started, despite the fact that the document has reached the predetermined portion, i.e., despite the fact that the effective scanning preparation has been completed. This undermines the high speed copying performance of the copy apparatus, reducing the number of copies produced per given period of time.